1. Field of the Invention
The present invention relates to an apparatus for fixing exposure and focus in a camera having automatic exposure control and automatic focus systems.
2. Related Background Art
In a conventional camera having an automatic exposure control system, an exposure fixing apparatus fixes exposure data for a specific composition. The exposure data includes a luminance value Bv, an exposure value Ev, a time value Tv, and an aperture Av. More specifically, the exposure fixing apparatuses are classified into two types according to the types of automatic exposure control systems. One exposure fixing apparatus, performs exposure fixing by inhibiting of storage data updating in an automatic exposure control system of a type wherein the time value Tv, the aperture value Av, or a combination thereof is derived from light metering results, and the time value Tv, the aperture value Av, or the combination thereof is sequentially stored. The other exposure fixing apparatus, performs exposure fixing by inhibiting of storage data updating in an automatic exposure control system of a type wherein the luminance value Bv or the exposure Ev is derived from the light metering results and sequentially stored, and exposure control is performed according to the stored luminance and exposure values Bv and Ev.
In a conventional camera with an automatic focusing system, a focusing fixing apparatus is a system which generally stops driving the lens at a given distance.
Conventional automatic focusing systems are classified into two types: in one automatic focusing system, functions for detecting just-in-focusing vs. out-of-focusing and for displaying detection results are continuously effected; and in the other automatic focusing system, the above-mentioned functions are not performed (refer to U.S. Pat. No. 4,422,746).
Each of the exposure and focusing fixing apparatuses to be described in this specification may be any one of the types described above.
Exposure and focusing fixing apparatuses in a conventional single-lens reflex camera are respectively provided with a first operation button for fixing exposure data associated with the automatic exposure control system and a second operation button for fixing the focusing position controlled by the automatic focusing system. If a user wishes to simultaneously fix the exposure data and the focusing position, he must simultaneously depress the first and second operation buttons.
If the user wishes to fix both the exposure data and the focusing position to take pictures by using a camera with the conventional exposure and focusing fixing apparatuses, he must depress a release button while simultaneously depressing the first and second buttons. The depression operation is complicated so that photographing errors may occur.